I managed to recover most of the material.

I came across this video on YouTube.

https://www.youtube.com/watch?v=bEm5mjSAppk

https://hetmanrecovery.com/hetman_pa...y_download.htm

Hetman Partition Recovery was able to recover 90% of the data from the flash drive. This is probably the best result so far. Overall, I'm satisfied because I managed to recover most of the data for little money.Thank you all for your help)