Translation:It takes ten days.
There are special pronunciations for counting days of the month, particularly 1-10, 14, 20, and 24. You can find the complete chart here: https://www.learn-japanese-adventure.com/image-files/t3-japanese-days-of-the-month.png
For the day counter, the tenth is pronounced tooka (too is pronounced like toe in English). To remember it, I think of ten toes.
I think "十日" of "十日かかります" is enough.
Because the verb is "かかります". It is fit "take". ("かかる" already imply it is "a period/term".)
Though I sometimes hear "十日間かかります。". Because it is not so strictry in conversation.
This person explained in detail. S/he insists that "十日かかります" is correct.
I can not find another comment now.
If you say 'じゅう', it is ten.
When you asked about 'じゅうにち', It had 'にち'. 'にち' is about 'date'. But you ask the case what 'when not refer to the date'. So I don't have an answer to the question. 'じゅうにち' is a just incorrect word. Native speakers don't use the word. At least I have never heard to use by adults. I hope your help. :)