Use Access' Query Designer. Select the Query tab, click on <New>, click on Design View and click <OK>.
In the "Show Tables" box, click on the tab_material table and click <Add>. Change the query type to Append Query. When Access asks you for the table to append, type in (or select) "tab_material_add." In the tab_material table field display, double-click on the asterisk (*).
If you don't have an auto-number in tab_material, the auto-number field in tab_material_add will increment nicely when you run the query, which is what you want. To run the query, click on the red exclamation point.