Because of their location and the need for specialized knowledge to safely access and replace them, I strongly recommend consulting a repair manual specific to your 2000 Tacoma 4-cylinder engine. This manual will provide diagrams showing the exact locations of the freeze plugs. Attempting to locate and replace them without this information could lead to damage to your engine.
You can find these manuals online (e.g., Haynes, Chilton) or at auto parts stores. The manual will provide valuable details including the size and type of plugs, as well as the proper procedure for replacement.