私はセブに3回行き、それぞれ1週間ずつ滞在しましt。って英語でなんて言うの？

If you want to express to someone that you visited Cebu three times, and each time you visited, you can express that in the following ways:-

1. I stayed for a week in Cuba, each time I went, and I've been there three times.
   2.I've been to Cebu three times and each time I stayed for a week.

2. I stayed for a week on each of my three visits to Cebu.
   Each of these sentences are straight-forward and easy to understand, and anyone of them can be used when you need to explain this to someone.

   Here are some examples of these sentences in use:-
   Example A: How long have you stayed in Cebu?
   "I stayed for a week on each of my three visits to Cebu.

The first phrase gives us two pieces of information, the first being that the person has been to Cebu three times, and also the duration of the visits.
The second phrase uses "visits" rather than "been to", and again the end of the sentence tells us for how long.
The third phrase puts the destination at the front of the sentence, followed by the duration of the visit. In this sentence the words "times" andoccasions" both refer to visits made to Cebu

It is actually a very straight forward sentence.
I hope the sentences help you to express your idea.

When you want to express that you have been to Cebu three times and each time you stayed for a week; then you may do so in the following ways:
-I have been to Cebu three times and each time I was there for a week
-I have been to Cebu three times. Each time I stayed for a week.
-I have been to Cebu three times and each visit was a week-long

In the first statement, you have stated that you have made 'three one week long' visits.This is the same as saying that each visit you made to Cebu lasted you one week.It's exactly the same as the second statement where you state that you have been to Cebu three times with each visit lasting one week.Statement number three is exactly the same as the first and the second statements except for a slight variation with the addition of 'so far' which means, 'up to this point in time'
So, you may say to someone:
I have made three one week long visits to Cebu.
or
I have been to Cebu three times with each visit lasting one week.
or
I have visited Cebu three times so far and each visit lasted one week.

When we say I have been to Cebu on three separate occasions, you are stating that each time you went was on a different trip.

I stayed for one week states the duration of your trips. We can say each time or each occasion. They both work perfectly and they are very natural

One week at a time:You say "at a time" after an amount to say how many things or how much of or how much of something is involved in one action, place, or group. I have been to Cebu three times and stayed for one week at a time.
In total: The entire amount of time that I have spent in Cebu is three weeks.