Dear Didier,
The reason why you did not get write access to your tablet’s files from your PC file explorer is that you did not specify how your USB connector should be used, when you plugged it to your PC.
So, as soon as you plug it to your PC, a notification should pop-up, asking you for how you would use it.
This leads to that form
Here, select “media device (MTP)”, and here you are… all your tablet’s files should now be displayed from your PC’s file explorer.