Greetings,
It's unclear if the problem is with the lens or the body. Like you said, I'd suspect the lens since you said it came apart on you. There's not much you can do by yourself. Sources says to try the following. You can try different orientations (pointing lens down). Gently tapping the lens on your palm to dislodge broken parts. Using reasonable but gentle force to twist.
Otherwise you'll have to have the camera serviced to remove the lens.
Canon stopped servicing the 5D Mark III in 2024. You might be able to find a private repair shop that can help. It really depends on how attached you are to the camera.
Canon is having a huge refurbished sale on bodies and lenses. If you've been on the fence about upgrading your gear, this would be a great time. There are lots of great deals, but one that is particularly good is the R5 regularly $2899 refurbished on sale for $2299.
Shop Canon Refurbished EOS R5 Body | Canon U.S.A., Inc. https://share.google/50FpDtiEAuxatbIud
~Rick
Bay Area - CA
~R5 C (1.0.9.1), ~R50v (1.1.1) ~RF Trinity, ~RF 100 Macro, ~RF 100~400, ~RF 100~500, ~RF 200-800 +RF 1.4x TC, BG-R10, 430EX III-RT ~DxO PhotoLab Elite ~DaVinci Resolve Studio ~ImageClass MF644Cdw/MF656Cdw ~Pixel 8 ~CarePaks Are Worth It
