I get three beeps, 2 short and one long, and then I get a black screen

Hello all,

I am using a Acer aspire 5742 and this laptop is fairly old, almost 7-8 years old. I keep having issues where I get the POST codes and then the laptop used to function properly but recently the POST codes come on but my laptop doesn't start up. I have an Insyde BIOS in case that helps.
I read somewhere that holding down the power button for 60 seconds and then booting up the pic works but it didn't for me.

I would really appreciate some help as I have some very important files on my laptop and I don't want to replace the motherboard during this time as all the shops are closed due quarantine and they tend to cost more too.

Cheers and thanks in advance.