Transfer Photos from old iMac to Mac mini M2 Pro

Hello! I am migrating from a 2013 iMac to a new Mini M2 Pro and am having a ton of problems. Migration Assistant totally failed (4 times) so I did a file transfer from my backup service (CrashPlan). (Sadly, my Time Machine also failed. It's all been a bit of a train wreck.) Most of what I need did transfer from CrashPlan. The most critical thing that has not come over is Photos. I have a gazillion photos, a huge file, so most are not on iCloud, either. Like I said, train wreck. Luckily, my old computer is still working. What is the best way to get the entire Photos library from my old iMac to my new Mini?

(Explain it like, well, like your are talking to someone in a train wreck. ;-) ) Thank you!!