Automatically add values in cells up to a set limit, according to varying criteria

[LexiaJB]

Hello! I would greatly appreciate your support with the situation bellow.

Column A – here I will add different serial numbers of different lengths; the maximum length is 7 characters
Column B – the maximum length of characters must be 7 for all the cells in this column; I need to add here a formula that does the following:
1. brings the values from Column A
2. if the values from Column A have less than 7 characters it automatically adds at the beginning of the string of characters the value "0" (zero), in each cell as many times it is necessary in order to reach the number of 7 characters.

Column A Column B
74323 0074323 (2 zeroes must be added in front to reach 7 characters)
4588996 4588996 (no zeroes added because the series in Col A already has 7 characters)
5463 0005463 (3 zeroes must be added in front to reach 7 characters)

I was thinking of a formula similar to the one bellow, only that I do not know what criteria to add to the concatenate function, is possible.

=IF(LEN(A1)<7, CONCATENATE("0",A1), A1)

[AliGW]

Why not just use custom formatting on column A to add the leading zeroes?

0000000

[JohnTopley]

With formula ...

=IF(LEN(A1)<7, REPT("0",7-LEN(A1))&A1)

BUT Ali's reply is better.

[LexiaJB]

Thank you very much for your help. In this case John's formula is perfect for what I need.
I forgot to mention that I can't change the values in column A because for future references I will need both the old series that will be introduced in column A as well as the new ones with the zeroes in front.