How can I get a date 30 days later from today?

I’m making an app for memorizing English words.
I have studied some words.
I want to see this word automatically again in 30 days.

To do that
I must first be able to calculate 30 days from today’s date.
I don’t know how.

And thirty days later, the thunkable compares to the date that the person is supposed to review today, and if yes, it shows the words we studied today.

To implement this, I want to know how to find the date after adding a specific day in today’s day. And I want to know how to compare dates. Find the distance between two dates.