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十日 is read as とおか and 二十日 is read as はつか.

二百十日 is read as にひゃくとおか (not にひゃくじゅうにち) and 二百二十日 is read as にひゃくはつか.

三十日 is read as さんじゅうにち or みそか, 四十日 is read as しじゅうにち or よそか, 五十日 (50 days/50th
day) is read as ごじゅうにち or いか, 八十日 is read as はちじゅうにち or やそか.

**Questions:**

  * What is the reading for 十日 in (一)百十日, 三百十日, 四百十日, etc.? とおか or じゅうにち?
  * What is the reading for 二十日 in (一)百二十日, 三百二十日, 四百二十日, etc.? はつか or にじゅうにち?
  * What is the reading for 六十日, 七十日 and 九十日 with 日 read as か?

**Edit:** It seems that some people may have missed the point. I did say "二百十日
(210) is read as にひゃくとおか (not にひゃくじゅうにち)"
([source](https://kotobank.jp/word/%E4%BA%8C%E7%99%BE%E5%8D%81%E6%97%A5-110043)),
so the claim that "We say とおか or はつか etc. only 十日 or 二十日, respectively."
doesn't seem correct. Likewise, 二百二十日 (220) is read as にひゃくはつか
([source](https://kotobank.jp/word/%E4%BA%8C%E7%99%BE%E4%BA%8C%E5%8D%81%E6%97%A5-592599)).
However, these two words seem to refer to very specific days that relate only
to agriculture, in that they form a period in which storms occur. That's why I
ask whether the readings とおか and はつか are still applicable for non-210 and
non-220 words, such as 110, 120, 310, 320, 410, 420, etc.

**Edit 2** : I also cited the 30, 40, 50 and 80 words, to make a point that
とおか is not _always_ used, given that in kansuji, these words are written as
三十日, 四十日, 五十日 and 八十日 respectively, all of which contain 十日 that's **NOT**
read as とおか.
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readings counters onyomi
二百十日 is read as にひゃくとおか. What about 百十日 or 三百十日?
1. As you expected, these can be read as とおか but it is not commonly used in daily life.

  2. Same as 1. => We say とおか or はつか etc. only 十日 or 二十日, respectively.

  3. 六十日=むそか (commonly ろくじゅうにち)，七十日=? (even Japanese don't know. ななじゅうにち or しちじゅうにち are used)，九十日=?

Special case (commonly used now):

  * 初七日=しょなのか (the first seventh day when the soul of a dead person comes to Sanzu no River)
  * 四十九日=しじゅうくにち (the day when the soul of a dead person arrive at paradise(極楽浄土).)

In a Buddhist mass, such ways of calling are used.
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As your links say, both 二百十日 and 二百二十日 are the names of certain folk
calendrical terms (210th and 220th days from
[立春](https://en.wikipedia.org/wiki/Lichun)).

Here, the date counter ～か is used to indicate a _day in the calendar_. Since
there is no serial date bigger than 31 in either Gregorian or Japanese months,
thinking about such big dates is usually meaningless. However, those specific
two words you mentioned are the only examples* that rightly represent that
definition: _210/220th calendrical day_ (of a year). You can either say that
those two are exceptional fixed expressions, or that you may use it when we
adopt an [ordinal date](https://en.wikipedia.org/wiki/Ordinal_date) system in
our daily life, but it is only hypothetical.

Besides that, you cannot use ～か form as a part of bigger numbers when
calculating days in general:

> 百[八日]{はちにち}間修行した _had training for 108 days_  
>  無人島に漂流して百[二十日]{にじゅうにち}め _the 120th day since cast away on a no man's
> island_

But 四日{よっか} is usable in any case, for some reason:

> 無人島に漂流して百二十[四日]{よっか/よんにち}め

* * *

* Unless you count in [十月十日](https://kotobank.jp/word/%E5%8D%81%E6%9C%88%E5%8D%81%E6%97%A5-583883).
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