How to backup data from tablet on boot up screen

So like the title says i dont know how to recover data from my tablet.

A month ago my tablet started having an issue where suddenly out of no where the screen turns black but like it is still powered on and i cant do nothing so i let the battery die and recharge just to have my screen after random period of use go black again , if i leave it without touching anything it wont go black though

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Also recently after hard reseting my tablet the tablet started not to want to boot up , until i try a milion different combinations of lock and volume up and down , thats how i found out about the boot menu , accidently clicked a few buttons and then it opened up a boot up menu and there were a few options one of which was backup data , and since i dont have an sd card that can hold that much data i literaly cant do anything , so i was wondering is there any way to backup all that data to my pc so that i can factory reset my tablet , or do i need to turn it on first in order to backup my data on pc? (I will add more things if i can remember or if they are of use)