Should one say
- 'the first 13 colonies on the planet Pelaton'
or
- 'the 13 first colonies on the planet Pelaton'?
Should one say
or
What you call "numerals" are in fact cardinal numbers, otherwise called cardinals (one, two, three, fouur, …); the set of all numerals consists, of the cardinal numbers and of the ordinal numbers (first, second, …).
The order should always be "ordinal - cardinal".
(CoGEL § 5.22) Ordinals cooccur with count nouns and usually precede any cardinal numbers in the noun phrase: • the first two days • another three weeks
"The 13 first colonies" and "the thirteen first colonies" is not found at all according to an ngram research (Google Books).
"First colonies" is not defined as the initial colonies that appeared in the USA; generally, it represents a number of coloniesin a time sequence or even in an "importance" sequence.
Here is an instance of the several ways this can be put.
(Report - United States. Congress. House) The depatment of the Air Force has made a complete investigation of this accident and has given consideration to all the amounts as set forth in the original bills, which were thirteen in number, and has made its recommendation as to the amount found equitable in each claim. (1951)
To amplify on another answer, neither phrase is correct; only “the thirteen original colonies” is correct, as there were no other colonies following the original thirteen, since the Revolution ended the ability of England to add more colonies and all of the existing colonies joined the United States. There can never be thirteen first anythings, only one. When we refer to the first thirteen somethings, it’s the set of the first, the second, the third… up to to the thirteenth something, not thirteen first somethings.