Text manipulation with Powershell

Hi, Its my first post and also my first step into Powershell.

I recent started to learn Powershell i want to shine at my newly joined company. 

We have a textfile that consist of Raw data like this

FILE.txt

1234,123456,12345,123456,1234,123

123,1234,12345,12345,1234,123456,

12,1234,123456,123,123,123

I would like to read that file and change the output like this (every , Seperate a new data)

so that every Data separation is 6 character long. 

1234XX,123456,12345X,123456,1234XX,123XXX

123XXX,1234XX,12345X,12345X,1234XX,123456

12XXXX,1234XX,123456,123XXX,123XXX,123XXX

Then i want to send the data to a new TXT file. 

Anyone got a tip to how i should start or what guides to check or if am lucky someone already has a similar script for doing this.

Also not sure it can be done with Powershell. So if it cant be done please let me know.