I need some more context but I will just write what comes to my mind.
"니까" means "because".
그는 잘 할 테니까 걱정하지마. (Because he will do fine, you don't have to worry about him too much.)
"텐데" is "would", used with the subjunctive mood.
내가 그녀의 번호를 안다면, 그녀에게 전화할텐데. ( If I knew her number, I would call her.)