So you moved your GIS data and now you need to update your MXD files with all those layers that point to the old data location.  What to do?  Use ArcCatalog to update them.  I’m using version 10.2 here.

First open ArcCatalog and navigate to the location of your MXD files.  Next, right click on one of the files and select “Set Data Source(s)…”

You can then edit your data paths by selecting the ones that need editing, then pressing the Replace button:

After you change the paths, make sure to enter a new MXD file name, then press the OK button.  That’s it!