Silver B came in both versions -- LP and NG. If it has a right side hook, right side weight scale, and a short hose with a big screw on plastic knob, then its an LP (or at least started as LP).
NG has no hook, no scale, long hose. Pictures below.
Some people would DIY convert from one fuel to the other, but not many. That is strongly discouraged. If yours is an OEM NG model, you are all good.
One great thing about these grills is that replacement parts are still readily available. You can buy parts new from Weber or other vendors, or scavenger parts from readily available donor grills. So if the frame and cookbox are in good shape, you should be able to keep it going for a long time. Years longer than most grills you could buy new today.
Weber Schematics - browse product schematics and part lists by entering a serial number, description, or by selecting a product family.
www.weber.com