Question lost onedrive files after installing m.2 windows boot drive

Mar 4, 2019
Here are my specs

so i recently bought the samsung m.2 drive after already having the seagate harddrive as my main drive. the m.2 drive i only installed just to have windows boot up on it for faster boot time. so after installing it and resetting up my computer i am having some major issues with my old hard drive. the seagate drive is recognized, its there, its just about full, but there are tons of files that i am not able to retrieve from it, including 7,000 pictures... the file folders are showing up as empty for those, yet i dont understand why the hdd is so full if those files are not even showing up on there. another example of some issues i am having is that i can not play metro exodus. it is in my hard drive i can see it but it will not open or install. this may be an epic games issue, as it does not show up in my epic games library.... no games show up actually. the main issue i want to resolve is where those pictures have gone. i found a progam online called EaseUs and downloaded it and that program was actually able to find all of my lost files on OneDrive on that harddrive. but they want 70 dollars for me to recover them. ive emailed microsoft, no help. if somebody has any information at all on something else i could try to recover onedrive files that would be awesome! please and thankyou!