Is 天的数月 the correct way to say "days of the month"?
&quot;一個月中的幾天&quot; might be the right translation

update
Now I understand your question!
If you want to list every days of the month, the answer might be

這個月有 (這些日子), 初一, 初二, 初三 ...
這個月有 (這些日子), 一日, 二日, 三日 ...
這個月有 (這些日子), 一號, 二號, 三號 ...

They are all right, but I prefer the second one or the third one
For example, if you want to list every days in February, it can be &quot;二月有, 一號, 二號, 三號 ... 二十八號&quot;