HOW transfer data from iMac to new Mac Mini

Here are the ways you can use to: Move your content to a new Mac - Apple Support

On your old iMac, run the free Go64 application to pinpoint the existing 32-bit applications, and drivers that will not be supported on macOS Monterey on your new Mac mini. For those that are found, check the individual vendor sites for versions stated to be compatible with Monterey. That also includes your printer/scanner/specialty drivers, as after nine years, the printer vendor may have abandoned support for it on Monterey.

Any 32-bit applications that arrive on Monterey will have their image imposed with the circle and slash indicating incompatibility:

Easiest is to make a Time Machine backup on the old iMac (which is something you should have been doing anyway since not having a backup is an accident waiting to happen) and use Migration Assistant to transfer everything to the new Mac.

Note: Make sure any of the apps you wish to move to the new Mac are compatible wit the Monterey operating system as well as being compatible with the new M1 processor.