That is quite the antenna for that little 4 watt mobile radio. Your antenna is rated at 1200 watts. You'll certainly be within spec on that one.
Both the antenna, and the radio, say they have SO-239 connectors. So you need a length of coax with a PL-259 connector on each end (which is typical). PL-259 is the connector that mates with the SO-239 connector.
The coax you need between these connectors is 50 ohm, not to be confused with the 75 ohm coax that you might see connected to a television cable input. Better cable is less lossy, thicker, stiffer, harder to work with and more expensive. So it's a trade off. The longer the cable run needs to be, the better the cable you should use. The less loss the better. Additionally, the power handling capability of the coax is of no concern to you given a 4 watt radio.
I am a newbie with CB radio and bought the antenna after a few too many
I kindof, maybe, almost, thought that a little. Don't forget about grounding and lightning protection. I'm no expert on that. But do read up on it. That's a pretty tall antenna you're got there (20 feet). It would be good to disconnect the coax cable from the back of your radio when a thunderstorm is approaching. Also, you want to waterproof the connectors that are outside. Water ingress is the number one killer of coax, and you're probably going to be shocked at how much this coax can cost. It's not going to be one of those $7 things you can buy at Amazon or Best Buy. 25 feet of connectorized RG8X is probably going to be around $40. The good thing is that CB radio is at low frequencies (HF) compared to mobile ham radios (which are typically VHF and/or UHF). And the lower the frequency, the lower the loss in the cable. So you shouldn't need extremely-low-loss cable for the frequencies you'll be working at, compared to what you would need for, say, HAM UHF frequencies if your cable run is long. In English (if you can call this English!) this means that you can probably get by with RG58 or RG8X instead of the much more expensive RG8. But if you're only at 25 feet, pretty much anything you'll be able to find with PL-259 connectors on it will work fine at CB frequencies (this is only my opinion, of course!)
Good luck! Be sure and report back on how your new setup works.