Transfer data iMac

Hello, laurencefromvalley village.

The best way to migrate data from an old Mac to a new Mac is to use a Time Machine backup created on the old Mac.

When you’re ready to setup your new Mac the easiest and most reliable way to migrate your data and files from the old Mac is simply to connect the old Mac's Time Machine external backup drive to the new Mac using a USB cable before you turn on the new Mac for the first time. You may need a USB/USB-C adapter for this; easily found at many resellers for ~$10 or less. 

When you start your new Mac for the first time it will launch Setup Assistant and lead you through the setup process. Eventually Setup Assistant will ask if you are migrating from another computer. You are, so select that option and follow the on-screen prompts to completion.

If you have already run and completed the Setup Assistant on your new Mac, then you can use the Migration Assistant application to move your data over. Connect the Time Machine external backup drive using a USB cable and launch the Migration Assistant app (located at Applications > Utilities > Migration Assistant). Then follow the on-screen prompts to complete the data transfer.

 Move your content to a new Mac - Apple Support:

https://support.apple.com/en-us/HT204350

i personally would use an external drive (HDD or SSD), connect it to the old mac and run time machine. then connect that drive to the new mac and use migration assistant to transfer your data to it. then you can use that external drive for a TM with the new mac.

how long will it take is impossible to say because you have not told us how much data you have on the old mac. nor do we know the specs of the old mac.

if you want assistance from apple to do that, please see: Contacting Apple for support and service.

EDIT: and, yes you would need to buy the TB cables first if you want to go that way.

When you buy a new Mac the easiest, quickest and most reliable method to migrate from the old Mac to the new Mac -is to simply connect the old Mac's Time Machine External Hard Disk to the new Mac using a USB cable before you turn on the new Mac. You will likely need a USB A to USB C adapter, you can find them on Amazon for $10 or less. When you start the new Mac for the first time it will startup Setup Assistant (SA), SA will get to a point where it asks if you are migrating from another computer, select Yes  and follow the on-screen prompts and it's done! It is THAT simple.

If you have already done SA on the new computer then simply connect the Time Machine External Hard Disk using a USB cable and launch Migration Assistant (MA) which is located in Applications - Utilities - MA. Then follow the on-screen prompts.

The ONLY difference between MA and SA is MA will create a new user account that you need to log into.

Both SA and MA migrate applications (not 32 bit apps) , data files, settings, it does not migrate Mac OS itself. Some professional apps such as Adobe and Microsoft apps may require re-installing their apps as they will not allow them to be migrated. As long as you kept the security keys for installing their apps, it is not a big deal.

Finally, please NEVER EVER use WI-FI to migrate, this will fail in almost 100% of the situations in my experience. WI-FI was never intended to move large amounts of data at one time.

thanks to rkaufmann87 and D.I. Johnson. i neglected to mention the difference between MA and SA.

Thanks to rkaufmann87 for saying not to use wi-fi

Thanks

jeffreythefrog :-) very useful advices ( are you a Prince ? )

you're welcome. and LOL, no, i'm not even remotely royalty. not even in my own mind. :)

Your welcome. Migration is extremely simple. Reread my instruction and it will not fail.