There are a few ways that you could accomplish this but I think the most simple would be to include some new recordsets on the page for these three tables that will be filtered by the id values from the select list.
You then need to update the insert to use the values from this recordset rather than the form values it is using now. This second part may require you to edit the code for the insert.
If these values are coming from three different tables then you should add in three recordsets, one for each table. They should be simple recordsets that are filtered on the posted values from their respective select list.
When you edit the insert you will replace the posted values with the recordset values for their label rather than the id's.