Keywords Ranking Milestone plan

Hi, I was working for SEO for one of my clients. For the last 5 months, he was paying 5k for pages. now he is asking me to suggest some plans and milestones on a fixed cost basis. Once that milestone is achieved, he wants to continue with the monthly plan. to maintain that.

3 keywords are there with the rank: 20, 77, one is not ranked.

To get these keywords on the first page how many months it will take?

help me with the milestone plan.

Thank you.