Best way to migrate files from a 2011 iMac to a new iMac

The fastest, easiest and most reliable way, is to connect the 2011 iMac’s Time Machine backup drive to the new iMac and Migrate from it.

see > Transfer to a new Mac with Migration Assistant - Apple Support

Note: you may also need a USB-C to USB-A adapter, if the new iMac is only equipped with USB-C ports.

I'd use a Time Machine type backup. But if that doesn't suit you simply copy all the pertinent data to an external drive and then copy it from that drive to the new device using Finder.