there are 2 phrases, the first only exists in the first week, in which you can only count the days as not even one week will yet exist, so for days 1-6 of sefirat haOmer, you will say:

Today is the [insert 1st, 2nd, 3rd, 4th, 5th or 6th as appropriate] day of the Omer.

from day 7 on, the phrase changes to include the count of the weeks as well, and it gets more complicated, for you have to keep track of the number of whole weeks and days:

Today is the [insert 7th…through…49th as appropriate] day, making [insert 1…through…7 as appropriate] week(s) and [1…through…6 as appropriate] day(s) of the Omer.

the actual counting phrase of the day will occur on that day’s main page, but should you have to count before that page is mounted, you have the formula here.