Do you read Japanese? You should say: 『昨日、カメラ屋へ行ったけど、欲しいのがなかった』 『昨日 (yesterday) 、カメラ屋へ行ったけど ((I) went to the camera shop but) 、欲しいのがなかった (they didn't have anything (I) want) 』 As you know, we express "When" at first, then "what you did". And you can omit the subject "I" when you talk about your own action. 　(I) went (there) but ； 「行ったけど」「行ったんだけど、」are spoken Japanese,「行きましたが」「行ったのですが」are written Japanese and polite for business conversation. Does this help you?

This is a large topic and cannot be covered here in one answer. Go here: http://www.guidetojapanese.org/learn/

thank you!

a conjunction

That needs a connective, the word for “but” like しかし、だが、けれども、ところが、けど、でも、がetc, and put one of those connectives in the middle between 2 sentences. As already mentioned, ｢行ったけど｣｢行ったが｣, and other than that, ｢行った。しかし～｣｢行った。だが、｣｢行った。でも～｣etc.