Translation:My house is between these houses.
It is as Thiagoleal says. If a plural noun doesn't end with -n or -s in the nominative, it gets an -n stuck to the end of it in the dative, e.g. for der Tisch (pl die Tische) it is auf dem Tisch (on the table) and, in plural, auf den Tischen (on the tables). Just keep in mind, that you might encounter singular datives ending in -e with some words, it's all but fallen away, but still remains in some phrases like zu Hause (at home) and nach Hause ([to] home, as in "I'm going home" (ich gehe nach Hause)).
And yes, masculine and neuter genitives usually get an -s stuck to the back of it, but I don't think you have to worry about those just yet :D
I can't say for sure as I'm still struggling to learn it too, but maybe this is the form the word "Häuser" gets when in dative. Some words, depending on the case, get this "bonus" form, if I remember well (in dative and genitive, I guess). Someone else might confirm it, but if you google for "german declension tables" or something like that, you'll find this possibility.
Actually, they add a suffix even if they end in -s already:
- des Hauses
- des Geheimnisses
Except for some ending-with-an-unstressed-syllable foreign nouns on -s.
- des Kompromisses (stressed, requires ending)
- des Journalismus (unstressed, no ending)
- des Atlas / Atlasses (unstressed, ending optional)
You can just use diesen or even den (dative of die), optionally followed by the determiner 'da', e.g. mein Haus ist zwischen diesen/den Häusern da (my house is between those houses [over there]).
There is a word 'jener' which means that (or those in the plural), but it's considered very formal, and you won't really hear people use it in conversation. Using the same example as above, it'll look like this: Mein Haus ist zwischen jenen Häusern.
in case you need it, the two-way prepositions :) http://germanforenglishspeakers.com/prepositions/two-way-prepositions/