I had some trouble figuring it out at first...
These are the two BNC connectors, Ignore the text.
This is an SO-239 connector- I have this on my J-pole
The SO-239 connects to the PL-259
See what you have and what you need, or tell us what you have and we'll tell you what you need.
It sounds like you need a BNC Male to SO-239 adapter... Not sure tho.