These are the two narrow ball bearings at the front end of the bottom tube.
(I believe it is advantageous to refer to part numbers instead of part names to avoid confusion.)
The silvery part below the black kickstand plate can be rotated for 180° - as it is asymmetric you can achieve several mm more space to tighten the belt - if necessary.
(Moreover that, there is still the opportunity to inverse the adjustment direction, if above does not solve the problem: How much play in Strida 5 belt? )