It depends on how you want to report it. AFAIK, there is no APA format for reporting LMMs.
Based on this reference, the author chose to report
p values alone. For example, he states:
The “Tests of Fixed Effects” table, Table 15.6, shows that grade
(F=12.9, p=0.002) and stdTest (F=25.6, p<0.0005) each have a
significant effect on a student’s reading score difference, but
treatment (F=1.2, p=0.289) does not.
As you can see, he reported it as
(F=25.6, p<0.0005) ignoring adding more details for the
Your second option is to report it the same way
F value is reported on APA style
F (numerator_df, denominator_df) = F_value, p = ...