Calculating eligibility based on date

Hello,
I'm trying to determine when an employee will be eligible for the 401k program. Employees can enroll after "First of the Month Following" 90 days of employment. I was looking to use a function that would allow me to fill out a cell with the exact date.

Example: if John Doe is hired on 3/2/2021, he's eligible to enroll in the 401k program on 6/1/2021. Enrollments can only occur on the First of the Month. I have attached a sample sheet with one desired result.

I searched through the database but could not find relevant with the keywords I used.

Much appreciated!