Help with switching physical campaign to online

So I've been DMing a 5e campaign, been playing in person, with a few of my buddies and we've run into some problems with people not being able to show up and overall difficultly meeting up so I wanted to try and switch to using Roll20 instead. But we are currently halfway through the Sunless Citadel adventure and I'm not sure if when we try to play online using the Sunless Citadel addon if we will have to start over from the beginning or if we can start from where we currently are and I can just mark the areas they've already been. If anyone knows the answer please tell me, being able to switch over to Roll20 would make playing more often easier for us. I'm not sure if this is where I should post this and if not I will take it down and post it where it belongs.

Hi Luke. It's no problem. You can start where you want to start, within the Sunless Citadel addon. Of course it will just require some reading and prep from you, the GM, to figure out which section of the adventure that the party is on, and place their Tokens in their current location. It should be a fairly smooth transition since you already know the paper module and Roll20 already offers the digital version set-up and ready to play. If you have any more questions, feel free to post and ask!