WordPress Update

Dealing with a long overdue Update for our site and just curious, being this out-dated, how long I can reasonably expect this to take with the development crew we have on retainer. I obviously don’t fully understand the depth of the situation and feel like we have a decently dynamic site considering the woocommerce and decently extensive back-end platform.. but we’ve been waiting on the update for quite some time and upon bringing it up, I’d like to get experienced thoughts on the subject. TIA