If you want to find inventdimid in axapta then you can try following code. This example also shows you how to create inventdimid.
 InventDim inventDim;  
 ;  
 // Set the values that you need for  
 // the journal or transaction  
 inventDim.InventLocationId = "01";  
 inventDim.InventColorId = "02";  
 // Use findOrCreate and use the inventDim  
 // variable that you have set values into  
 inventDim = InventDim::findOrCreate(inventDim);  
 // Use the inventDimId to link to the  
 // InventDim record that was either  
 // found or created  
 info(inventDim.inventDimId);