Airpump for fish?

Recently my daughter got some fish from a fair. I got her a 3 gallon tank 2 small decorations and a water filter. Didnt read instructions on water filter bought from petco the Aqueon Betta Filter with Plant,(linked below) and noticed it requires and air filter. Im not seeing that air pump that would go with it does it matter, do you sell the air pump for them? I dont want to return the product i rather just get the air pump it requires.

( https://www.petco.com/shop/en/petcostore/product/aqueon-betta-filter-with-plant-3171868?store_code=1842&mr:device=c&mr:adType=pla_with_promotionlocal&cm_mmc=PSH%7CGGL%7CCCY%7CCCO%7CPM%7C0%7CaxsvnXfjRWFFwpetHmZu75%7C%7C%7C0%7C0%7C%7C%7C21467366052&gad_source=1&gclid=CjwKCAjw59q2BhBOEiwAKc0ijaZkDaGPQF8CREJqf-xqa_GKwxho2W3jxxcdUSK2n64Dowz0hCRZIxoCNiIQAvD_BwE&gclsrc=aw.ds )

Thanks in advance .