First step is to check line from tank to pump. You probably have a shut off valve under the tank. Turn that off, disconnect line at each end and try to blow air thru the line to the pump. If that's clear open the gas tank valve and check for flow. If that's good you're left with the pump and line to carb. Check pump by connecting hose to output (after you've reconnected the line to the tank and turned valve on), have someone crank the engine and look for output from the pump, using a catch can. That should tell you if there's a problem in the fuel system and where it is. Most guys run a filter in the main line from the tank to the pump since tanks are old and have lots of sediment.

Ed