Joe Giudice says money goes a long way at Fort Dix — the minimum-security prison where Diddy’s now doing time — and it can make life a whole lot easier behind bars.

The former reality star — who did hard time there from 2016 to 2019 — tells TMZ inmates are “all about money,” and says Diddy could even dodge certain responsibilities if he’s willing to cough up some cash … like his new gig in the laundry room.

Joe says he used to pay other inmates to do the chores he didn’t want to do — including prison work — and claims Diddy could easily slide someone a few bucks to mark him as showing up for his job.

TMZ broke the story … Diddy began serving his 50-month sentence at the New Jersey prison on Thursday — the facility his lawyers requested so he could “address drug abuse issues” and “maximize family visitation and rehabilitative efforts.”