Simply put, you can't. An array of anything (even a cell array) has to be regular (your cell array above is Nx1; it is only the content of the various cells that have a different length by alement).
You can only augment the shorter rows with NaN or other values to the length of the longest record in order to save the input file data shape and have a double or other numeric array.
If you would provide some indication of what you need/want to do with the result, folks could probably give you hints on how to write code to efficiently handle your data.