@Molly makes a good point about IT/network security policies, but given that you have only the company's best interests in mind:
I, for one, am not entirely clear on which PC you want to access from where...
- Your home PC while sitting at your work PC,
- Your work PC while sitting at your home PC, or
- Your database server (at work) while sitting at your home PC.
All three are very possible (disregarding the potential for explicit routing restrictions from your IT department). You mention that IT already has a VPN server running, so presumably your home PC is running a VPN client and is already connected to your corporate network.
If you simply want to use your development tools on your home PC to work on the database at work (rather than remoting into your work PC; I prefer this too), you should already be able to do so if you know the database server's IP address.
(But, I'll be the first to admit that I may have misunderstood your objective.)
EDIT: Adding my reply-comment to the Answer itself:
So, if I understand correctly you want to know your local (VPN) IP address so you can add it to the list of IPs with access to the DB? If that's the case (and you're in Windows) you can do
ipconfig in a CMD window to see your locally-assigned IP addresses. Find the one for the VPN's virtual adapter.