geolocate iPad via Dropbox activity
While you can sometimes geolocate an IP address (which you can find out from Dropbox on the website by clicking the account name, settings, security, and the "i" by the relevant device) and typing this into an IP geolocation service, it will not usually show you a location anywhere near where that IP address is in use. In fact different services can report completely different locations.

The IP could be used by the police to request that information from the ISP themselves with a warrant though as they will hold records on where it's currently in use, and would be by a single location.

There are some caveats though, the IP could be a public hotspot, or a company which allows VPN access which means it could be anywhere.

All Dropbox can give you is the IP and hostname of the device though, so unless you're able to take it through the route of legal proceedings, it's unlikely.