I was cleaning my hasboards and dropped one of them, the impact caused two to fall off.

I have attached two pictures.

How do I go about cleaning the current heatsink and hashboard chip prior to correcting?

Which thermal paste is considered the best for this job?

https://i.postimg.cc/mBZPwtHs/20220330-122238.jpg

https://i.postimg.cc/QMgjqQ3w/20220330-122244.jpg