Hi how many pr2- pr7 backlinks does it take to rank high for serps in keyword forum would 300 be enough to make it in top page?
for the keyword 'forum'? If so, 300 wouldn't be even close. You would need 1000s of backlinks because the term is so broad and competitive, these backlinks would have to have varying PR also.
Man, don't waste your time trying. Even if you succeed it gonna be useless. Think, how many people type "forum" in Google!? You are better to go more specific and take over some niche.