"I have 10 datasets named data1, data2,data3,...,data10"
Numbered variables are a sign that you are doing something wrong.
Trying to access variable names dynamically is how some beginners force themselves into writing slow, complex, obfuscated, buggy code. Read this to know some of the reasons why:
You should use indexing. Indexing is simple, neat, easy to debug, and very efficient (unlike what you are trying to do). You can trivially use idnexing to put your data into one cell array when you load/import the data, then you can simply do this:
A = cat(5,C{:})
Better data design lets you write simpler, neater, more efficient code.
