How to transfer 68000 photos from Mac to a hard drive?

Move your Photos library to save space on your Mac - Apple Support

Export photos, videos, slideshows, and memories on Mac - Apple Support

To learn how to connect and use an external storage device (flash drive, CD-ROM, hard disk) for general purpose file storage (including photos) read

Connect and use other storage devices with Mac - Apple Support

Erase and reformat a storage device in Disk Utility on Mac - Apple Support

Flash Drives are not reliable for storing photos and burning photos to CD's is impractical.

What you need, is an external drive that is large enough to hold more than 68,000 photos.

If the photos are organized and managed in the Photos App...?

Have a look at > Move your Photos library to save space on your Mac - Apple Support

If the photos are scattered about on your Mac like rocks on the moon..?

You will need to manually locate the photos, then drag & drop copy them to the external drive.

Then you will need to manually delete the photos from the Mac, after they have been copied to the external drive.

If your intention is to use a CD or Flash drive as long term storage this is a VERY VERY bad idea as both types of media deteriorate over time and the photos will eventually be lost. Please use an External Hard Disk for long-term storage using the most up-to-date connection method available (USB C).

Then simply organize the photos into folders (years, events, etc...) and copy and paste to the External Hard Disk. A great solution would be something like the OWC Ultra Express 1M2, https://eshop.macsales.com/shop/owc-express-1m2

Just determine the amount of storage you need, buy the drive and copy and paste away!

Ignore earlier posting. Misread the intention.

You can either copy the entire library go the eternal drive (the drive MUST BE formatted as APFS for SSDs or OS X Extended (journaled) for HDDs) or export as JPEGS with the options to include all metadata to a folder on the external drive. It would be best to sort by year and export in smaller groups.

Please read the following user tip and restate your question/problem in detail: 

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What model and year Mac do you have?

What system version is it running?

Are the photos on the iPhone in the Photos library?

IMO the easiest way to transfer all of the photos from your iPhone to your Mac or an attached external drive would be to use Image Capture which comes with all Macs. You'll need to connect the iPhone to your Mac with its USB charging cable and launch Image Capture. Then you can select the destination location.

I have a library with 54,787 photos and 899 videos. None are Apple's HEIC or HEVC. The size is 183 GB so a 400 GB or 1 TB external drive would be sufficient. I'd go for the 1 TB size.

If budget is a concern you might try this type of setup:

Most likely the same way they get there... Updoad to Cloud, and download to another device that can use a flashdrive or other backup drive.

You will also want to make sure to back up all those photos stored on external media if they are your only copies.