How can I unlock my Acer tablet code. I can't do anything.

I can't remember my acer B1-770 tablet unlock code. I can't do anything.

When I switch it on, it will ask for me to draw my pattern that I can't remember. What can I do? The shop where I purchased it, they can't help.

I have tried to download drivers to my micro SD card for me to set it to factory setting. Nothing worked. When I press volume up and the switch, it gives me this message => FASTBOOT mode...

Any help.