For the Apache license, one requirement of the license is that recipients of the work receive a copy of the license:
Redistribution. You may reproduce and distribute copies of the Work or Derivative Works thereof in any medium, with or without modifications, and in Source or Object form, provided that You meet the following conditions:
You must give any other recipients of the Work or Derivative Works a copy of this License; and ...
If you did not receive a copy of the license, then I would argue that based on the license itself, it is not a valid way to license a work under the Apache 2.0 license. If all you received was a file called package.json that contained a line such as
Then this does not fulfill the above requirement ("you must give any other recipients of the Work or Derivative Works a copy of this license"). Based on the license itself, this is not a valid way to license a work under the Apache License.
What do i need to do if i want to edit any of these files?
You need to get a valid license. If you have communicated with the author and he has actually told you that the license is valid, that it is indeed under the Apache-2.0 license, then perhaps that would be sufficient. But in this case, to redistribute the work under that license you would need bring the files in a state that follows the requirements listed in the Apache license under "Redistribution". In particular, you would need to give any other recipients of the Work or Derivative Works a copy of the Apahce 2.0 license. You would also need to follow all of the other requirements of section 4 of the Apache license. For example, you must indicate which files you changed:
b. You must cause any modified files to carry prominent notices stating that You changed the files; ...
See: Apache License 2.0