https://blockchain.info/tx/31dd549bdd6a3f783ad4906d3baaa1859efe398ddd57e8356ce6dd197114fd91
It's not really a fixed number.
For example look at your transaction it had fees of 0.0002871 BTC
But still took more than 2 hrs.
It depends on how the bitcoin network is congested or not.
It's best to leave the fees blank (to be selected automatically by the client) depending on the previous transactions.
There are actually much info about this on the internet like calculating the transaction size (in bytes) then selecting a suitable fee, but in my experience none of that turned out to be really accurate or helpful to me.
Anyway, good luck and happy to see your coins settled finally.