What are you hoping to achieve by confronting him?
I really do understand the need for 'proof' before you end a relationship but you have had proof that he lies many times.
It's generally not a good idea to check someone's phone but you checked because you had suspicions. Not because you're paranoid but because you, what? Recognised a pattern of behaviour you've seen before? Something didn't add up? It was confirmed he wasn't where he said he was?
If you confronted him and he denied it, would it change the truth? If you confronted him and he admitted it, would you leave then?
Do you want a tearful apology that would make you feel heard, understood and safe again until next time?
I'd work backwards from the outcome you want.
If you're going to stay with him regardless, then there's little point in confronting him.
If you'd leave him if he admitted it, then you already know the truth.
If he tells you she's 'just a friend', then why lie about helping her? Or do you just want to hear a lie you can 'accept'?
Tbh in your shoes, I think I'd be at the stage where I'd just be honest and tell him I'd looked.
"I looked at your phone because I know you weren't where you said you were. Given you have a history of lying, I wanted to see for myself and you had, indeed, lied," or similar. But you need to know what you want the outcome to be before you do.
But if you confront him without admitting you know the truth, he's just going to lie to you again. Because he's a liar.
Tbh, this is all theoretical because I'd have walked away a long time before now.