Block Difficulty

Hey, stupid yet simple Question. What share difficulty is needed to solve a block solo (just looking for a solid hash difficulty answer, like 50T for example.) The network diff says like 33k, but since the solo mining share diff on 2miners is 4.295G (and they obviously don't solve a block), would someone be kind enough to tell me what difficulty is needed to solve a block? (Bonus cookie if you also explain what the 33k Network difficulty means)