If you mean the Preferred Qualifications for the job contains something like
Upwork Hours: At least 100 hours
then the client prefers freelancers who have worked 100 hours or more at Upwork on hourly jobs. The only way to get the hours requested is to do enough hourly work for clients who don't require that many hours. You can still apply for a job if you don't have the number of hours specified but as you found out, your proposal might not be accepted.
"No good deed goes unpunished." -- Clare Boothe Luce
One of my first jobs I applied for had x amount of hours on Upwork, which I didn't have but I put in a purposal anyways. If you have previous skills and you feel you can do the job ad express it in your purposal there is no reason to let it deter you, although with some of the algorithms not sure if you will even get seen. Not sure if they are still hiding purposals.
But if you have all of the other skills and you don't mind spending the credits take a chance.