I have some experience with migrations. What I can suggest is the following.
FIRST and very first, create a product oriented work breakdown structure. Don't do this alone, do it with the support of the team.
About the WBS, I'd put in the first level of my WBS the following:
Website: So you can decompose further the features to deliver (frontend, ...
If you have already started the sprint - i.e. its an active sprint and you want to see the 'burn-down chart' in hour instead of story points, then you can go to the settings of the board in Jira you can change the burn-down to look at hours instead of story points.