Save your player data with ProfileService! (DataStore Module)

How do I go about adding a new value to a profile without messing with data.
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I am adding levels to my game and need to make it save with profile service, while not messing with my other values.

“levels” is currently nil, and I can check if it is nil with an if statement. Where do I go from after confirming that it is nil, so it saves the levels and doesnt end up with this error:
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