lots of good advice already, my 2 cents: open the pack you have. get some new heat shrink and carefully open the pack you plan to copy. you should be able to pull the shrink and then the fiberglass sheets to get a good look at the pack you have. then take some photos and post them up. if you’re not familiar with the build method I’m sure someone here can shoot you in the right direction to get good supplies for your build.
if this is your first build and you haven’t found the wiki:
it has some good general info and stuff.
there are also quite a few battery builds posted up here with a little searching that have tons of pictures showing how to use and make custom nickel strips for odd/complicated pack layouts like the one you are planning.
I also found it helpful to use a 3d cad program to do the cell layout - if i don’t see it it is hard for me to visualize. something like tinker cad or mater control are free and can be learned pretty quick if you haven’t messed with 3d printing and know them already. just make a cylinder in the correct dimensions and start fucking around… or when you get the cells grab some masking tape and just start arranging them - when they are at shipping charge level and not connected in parallel yet they are relatively safe to play with as long as you take basic precautions not to short or damage them