Since you have Mike Urban installed, you should have a copy of ArcGIS Desktop, which is probably the best tool to shift the model elements in (assuming the model isn't small). Assuming your model isn't too complicated, just:
[li]open ArcGIS Desktop[/li]
[li]add the msm_Link, msm_Node, msm_Weir, msm_Pump, and msm_Orifice layers from your model[/li]
[li]start an Edit session (Editor > Start Editing)[/li]
[li]select all the elements[/li]
[li]move the elements[/li]
[li]save the edit session (Editor > Stop Editing)[/li]
You may want a base layer to know where you're moving them. If you want to be more precise, there's a bunch of editing tools in the Editor toolbar and geoprocessing tools in the ArcToolbox included in ArcGIS you can look into that can accomplish more precise adjustments.
If you can't edit in ArcGIS Desktop for some reason, some other options include:
[li]edit the coordinates in the source MEX File (it's a text file), assuming that's where you got the MOUSE model...if you're used to US units, they're generally in metric (which..thinking about it may be why you're model shifted in the import process. Assuming that's the case you can probably set the Mike Urban units to all metric and retry your import; if you don't retry the import you'll want to make sure you didn't mess up the length of each element, as this will impact hydraulic results by a factor of like 3.28x)[/li]
[li]use the import/export tool to get to a format you can work with[/li]
As to where the coordinates are stored, Mike Urban models aren't just Access databases; they also conform to the ESRI personal geodatabase format. I haven't found a good specification for personal geodatabases (like there is for shapefiles), but from hunting around I believe the coordinate data is stored in the SHAPE field in a binary format. You could think of it a little like a linestring. If you really want to get a copy of the coordinates, in ArcGIS Desktop you can add a new field to the attribute table for the layer and "Calculate Geometry" to populate the new field with the X coordinate, Y coordinate, etc.