If it won't, I'll let you have my copy that I bought on a whim when it was offered for 80 bucks at the App Store!
It sounds like you may have a PPC version. If so, it will not run on the new hardware, no matter what OS you put on it. If you still have an operating PPC machine or even one running 10.7, you can open System Information (click on the 'Apple' icon in the Menu Bar and press the option key, is the easiest way to open it) and select Software->Applications in the left-hand list of things. I'm already on
Mavericks, so what I see in that app is different now, but I think will eventually see a list of all your apps and there should be a column named "Kind" or maybe "Type". That will indicate if it is a PPC/Universal/Intel/etc. app. As I said, if it is "PPC" it simply won't run on the new hardware.
If you got it via the App Store, you should be able to simply update it. If you bought it in a different manner, you may be able to 'sweet talk' Apple into letting you download the new version, anyway. Last resort, of course, would be to buy it, it's still less than $80 ($79.99, to be exact!).