 So you have old animations from Unreal 4 that you want to use with your new Unreal 5 skeleton, not a problem. Assuming you bought the new pack from the market, add to project, pick your project, add, wait for it to load and you should see it appear in your project. Then find all the old Unreal 4 animations, select the ones that you want to translate, right click, retarget animation asset, duplicate and retarget animation asset. Change none to UE4 and UE5 Mani and under change, pick the folder where you want the translated animations to be exported, retarget, you're done. Hope that helps and as always, hope you have a fantastic day and I'll see you around.