From the launcher, it will ask if you want to update the store, as opposed to your game. There was an earlier store update and then a second one. I'm not sure what they did, but any store content after that patch would not install unless you patched with the store patch.
Look here: https://www.thesims3.com/store/patches
version2.2 is the latest store update
Again, if you don't need to reinstall, then, you don't need it. But, I'm not sure your store stuff will reinstall without it. So, if you are reinstalling, the launcher has a better chance of updating BEFORE you put anything in it.
Ah, here:
To install this update, please start your game and use the “Downloads” tab in your Launcher. This Store update includes the following changes:
Updated appropriate clothing to be selectable as Outerwear when playing with The Sims 3 Seasons.
Disabled random selection on some pieces of clothing so Sims won’t use them unless specifically directed to.
Fixed an issue where users were not seeing the cake slice that came with the Happily Ever Frosted wedding cake in Monte Vista.
Fixed an issue where users were missing several Create-A-Sim assets, including the La Dolce Vita Updo and Tuscan Hat from Monte Vista.