https://www.lifewire.com/find-phone-number-online-3482154
From general search engines to more obscure (and focused) websites like Zabasearch, the websites on this list will help you find a phone number for free.

https://www.reddit.com/r/questions/comments/1364lo2/is_there_a_way_to_find_someones_phone_number_with/
I only know their full name and address, and was wondering is there anyway I could find a phone number linked to this?

https://callhippo.com/blog/general/how-to-find-someones-phone-number
TruePeopleSearch This website lets you search for people by name, phone number, or address. It provides details like phone numbers, addresses, ...