Welcome to the forum.
Thanks for your reply Aldav,From what I can see the Trend universal sub-base doesn't accept Porter Cable style guide bushings so you'll need purchase a Trend guide bushing. If you want to use the industry standard Porter Cable style bushings you would have to get an after market base that accepts them, these bases are readily available. As to what size bushing to buy that will depend on the type of work you're wanting to do with it. Is there a particular reason you want a metric bushing?, most router bits are imperial.
Thanks SReilly,Maybe a better description to use would be what you are trying to accomplish. Are you trying to cut a particular sized slot with the 1/4" bit or use a template to trace something? BTW, welcome to the forum.