How to renumber large excel file with blank spaces between

Hi i have a large excel file with thousands of rows of data. I want to renumber the data whilst having a value of 10 between each in the format M00010,M00020,M00030 etc. These values are all in column A and where i have an M00010 value in column A i have a Text string in column B. Between the values in column A i have different numbers of blank rows that i need to keep. Sometimes 2 sometimes 3 or more.

I have tried using Filter but this doesn't really help as i can't use FILL to change the numbers.

Any help would be appreciated.