Backlight probably died if it's an old LCD style one. Or the invertor. either or, not worth fixing.
It has worked up until that last time I turned it on which was a few weeks back, is it still the same problem? And even if it is dead, is there a possible way I can fix it? Or do I have to get it fixed?
First you said you haven't used it in a very long time, and now it's a few weeks back.
A dim screen means the light that lights up the back, isn't working. Either bulb is blown or the power invetor that creates power for it has blown, which is probably the case. In reality, I doubt anyone could fix it as the part would be non-existent to find anywhere. Buy a new one or a cheap phone or tablet or something.