Curing a pumpkin?

Sorry to hear you had produce stolen - that's really low of someone.

You need to get the skin toughened up for storage.  I assume its started changing colour    If so, I would put it somewhere where the sun can get to it, but its off the ground and protected from the weather.  I usually use the greenhouse staging.

I've done this with less than ripe fruit at the end of the season where I don't dare leave it outside any longer and it doesn't store as long as naturally ripened fruit, but does still keep  

I'm not sure to be honest, but if its that green I would try a window where it gets plenty of light but not too much direct sun.  If the skin is soft, too much heat, especially magnified by glass, might start withering it rather then ripening 

As I said I've picked fairly under-ripe squash just because there was a chance of saving them, but that was later in the year when the greenhouse had cleared a bit and the sun was not so strong.  I put mine in trays on the staging shelf and moved them up to the top later when they were riper and the skin felt it had hardened

I had a load of small ones last year (can't remember the exact type), but when they were a little orange, I gave them a (very weak) bleach wipeover, then put them on my dining room table which lives in front of the window and they all ripened nicely.