Post-hoc sub-ANOVAS on ezANOVA - how to correct for multiple tests

Question

Using a dataframe which looks like this (with 3 raws per "id"):

data_rt = data.frame (id  = c("sub-a", "sub-b","sub-c","sub-d","sub-e","sub-f","sub-a", "sub-b","sub-c","sub-d","sub-e","sub-f","sub-a", "sub-b","sub-c","sub-d","sub-e","sub-f"),
                 group = c("group1", "group2","group3", "group1", "group2","group3", "group1", "group2","group3", "group1", "group2","group3", "group1", "group2","group3", "group1", "group2","group3"),
                 session = c("session1", "session2","session3", "session1", "session2","session3","session1", "session2","session3","session1", "session2","session3","session1", "session2","session3","session1", "session2","session3"),
                 rt = c("60", "160","13", "10", "150","200","15", "42","69","47", "160","90","60", "35","30","209", "15","12"))

I performed a 2(cond1, cond2)x3(group1, group2, group3)x3(session1, session2, session3) ANOVA like this:

anova_rt = ezANOVA(data = data_rt,
         dv = score,
         wid = id,
         within = .(condition, session),
         between = group,
         between_covariates = .(age, iq),
         type = 3,
         return_aov = T)

I got a significant three-way interaction. To do post-hoc, I assume I have to do sub-ANOVAS (e.g. one ANOVA per group to see the effect of session in each group). How shall I correct for these additional 3 tests?

Thank you!