How To Use Find / Replace In Formula

I really would like to alter about 1000 lines of formulas. Here's a sample of the code.

Code:
=IF(COUNTBLANK($AE$6:$AE$7),"",MIN(U7,AD289*$AE$37))
=IF(COUNTBLANK($AE$6:$AE$7),"",MIN(U8,AD290*$AE$37))
=IF(COUNTBLANK($AE$6:$AE$7),"",MIN(U9,AD291*$AE$37))
=IF(COUNTBLANK($AE$6:$AE$7),"",MIN(U10,AD292*$AE$37))
[Code] ....

*****The last line of code is below*****
=IF(COUNTBLANK($AE$6:$AE$7),"",MIN(U966,AD1248*$AE$37))

What I'm really trying to do is replace all the numbers (well, max of 3) after the U part to U6.

So,, for example ,, if in the code it shows MIN(U16,,,,,,,, I want it to show MIN(U6

So as an example

Code:
=IF(COUNTBLANK($AE$6:$AE$7),"",MIN(U966,AD1248*$AE$37))
WILL NOW BE
=IF(COUNTBLANK($AE$6:$AE$7),"",MIN(U6,AD1248*$AE$37))
So U6 is in all the formulas.

I've tried searching on google,, saw a video here on UTube;
Excel Magic Trick 519: SUBSTITUTE & REPLACE Functions
[URL] ........

Showed some great stuff,, but I just didn't quite get it for the above.