It isn't a stupid question at all.

Does it still smell like fresh soil or is it musty smelling? The problem may be a fungus if it was stored too moist. You can bake it (smelly) at a low temperature to kill any fungus - or spread it out in the hot sun for a day or pour boiling water through it to kill any fungus. If it smells okay, you could plant a few plants in it to see how they do and if they are fine, go ahead and use it. If it were me and it smelled okay, I would put it at the bottom of the containers and put fresh soil on top (or just mix new with the old) Be sure to mix some perlite in (even new soil) so fungus doesn't grow and you don't get a fungus gnat problem.

Do a google search (link below) on sterilizing potting soil

Here is a link that might be useful: potting soil sterilization

Welcome back gardening!

In my experience, it's probably more likely that the soil has been extensively dried out... if this is the case, the good microbes may be kaput... but no worries!

My recommendation is to mix the old soil with new soil, perhaps from 1/3 new to 2/3 old. This will help inject a new batch of microbes and fresh nutrient to get you started again.

If it is musty and you do try to sterilize it, you should definitely mix it with new soil afterwards.

Thank you both very much! I'm off to sniff my soil and will purchase some fresh soil to mix with it!