Hello,
Thanks for contacting us and we regret the inconvenience caused.
You’ve not created the RegEx expression correctly.
If you want to redirect all the links having /telechargements/ to /wp-content/uploads/, then please try creating the redirection with the below expression:
Source: /telechargements/(.*)
Type: Regex
Destination: /wp-content/uploads/$1

Please let us know how that goes.
Thank you.
Hello,
Since we did not hear back from you for 15 days, we are assuming that you found the solution. We are closing this support ticket.
If you still need assistance or any other help, please feel free to open a new support ticket, and we will be more than happy to assist.
Thank you.