How do you say i like you in french language?

There isn't an exact equivalent between languages.

If you want to say "I love you" you can say "Je t'aime" or "Je t'adore".

If you want to be less forthright you could say "Je t'aime bien", which means "I like you" in the sense of "I am fond of you".

Or "Tu me plais" means "I like you" in the sense of " I like the way you are" or " I find you pleasing", BUT it can also mean "I find you attractive sexually" or " I fancy you", so it can lead to difficulties.

A safer option might be to say "Je te trouve sympathique", as this means you like the person in a more general fashion - and it has no other connotation.