I know (Phil 1:19)

Philippians 1:19

[yes, and I will rejoice] for I know that through your prayers and the help of the Spirit of Jesus Christ, this will turn out for my deliverance, 

When Paul talks about deliverance here, is he talking about being released from prison? Maybe, but he knows that ultimately he will be delievered

"I do know that that what I'm going through now is temporary and the future holds my deliverance, whether it's vindication in court, release from prison, well-being, or eternal heaven, I'll be delivered out of this." McArthur

How does he know this so confidently? Because of God's promises, God's word. Paul is quoting Job 13:16 - echoing that we might not understand our suffering but we know that God is working through it. He is also confident because of their prayers for Him and dependance on the Spirit. If he was only depending on himself or on his friends or the church then the full confidence of deliverence may not be there. But we can trust that God will do what he says through the Spirit.

Rom 8:28 For we know that in all things God works for the good of those who love Him, who have been called according to his purpose