mainframe signed to numeric format outside mainframes

I am receiving data from mainframes in the format below,

123D1234123456G12345678I
123M1234123456G12345678I
The mainframe team is telling the data they sent using FTP is below,
123412341234567123456789
-123412.341234567123456789

They are not providing any other information.

I receive huge data in this format.How can i get the details they are sending to me using VBA function or macro?

Many thanks in advance!

Thanks for the short response! What should be asked?

Originally Posted by shg

The question you want answered: How to interpret the representation of numbers.

They don’t know