"Thus, i would like to change these variables to be only number."
Valid variable names must start with a letter, they cannot be "only number".
The easiest solution is to avoid this problem entirely by load-ing into an output variable and accessing its field/s:
S = load(...)
You could then use struct2cell to trivially access the field contents, and place these into one array (numeric, cell, etc) using basic MATLAB indexing. Note that it is actually much easier to process a sequence of .mat files if they contain exactly the same variable names, because then these can be trivially imported into one non-scalar structure, and accessing using simple, efficient indexing.
