@crayfish actually answered it above but you have to click the link:
～てなんぼ , where なんぼ is a kansai-ben version of いくら) is a little slangy set phrase that means “to be worthy only if ～”, “to be meaningless without ～” or “to be all about ～ing”
More specifically:
バレーボールは繋いでなんぼ大事のは - the important thing about volleyball is that it’s all about “connecting” (roughly translated)