Uds. cortas a su abuela cada mrs. (mandar)

This sentence should be:
Ustedes mandan cartas a su abuela cada mes.

Translation:
You(formal) send letters to your grandma each month.

Ustedes- you(formal)
Mandan-send
Cartas- letters/cards
A su- to your
Abuela- grandma
Cada- each
Mes- month

The sentence you provided was grammatically incorrect since cortas means to cut and Mrs. is used to introduce a married woman which should have been mes which means month.

Hope this helps! :3

Can u give me a link to the video so i can answer your question

What are the words from the list