You cannot specify "120 days". Your options are past 60 days, the current calendar year, the post calendar year, and the one before that. The last 120 days would all be included in the current calendar year since this is the latter part of June.
Go to My eBay: Purchase History
On the top section ("Orders") change the See orders from: to 2021
ETA: If you absolutely must has a list limited to the past 120 days (or some other period) there is a way but it it is far from instant (I think it takes about a day to get the report):
You can make a special request for a report of your purchases (and/or sales and/or lots of other information) for a specified time period back to the creation or your account (and possibly any guest transactions if you provide the right data): https://www.ebay.com/help/account/requesting-personal-data/requesting-personal-data?id=5089&st=12&po...
