A few thoughts you may find helpful.
Remember to distinguish between a demonstrative pronoun and a demonstrative adjective. For example 'those are young boys' (pronoun) vs. 'those boys are young' (adjective). In English the same word 'those' is used for both, but in Czech different words or different forms are used for each.
In Czech, the singular 'to' can be used even when talking about plural items. So, for example, the Czech sentence here, "Jsou to noví lidé", is literally "It are new people." In any case, remembering my first point above, here "to" is a pronoun, not an adjective.
When translating a Czech plural demonstrative adjective, the choices in addition to 'those' include 'the' (those boys = the boys).
But when translating the Czech demonstrative pronoun, the choices in addition to 'those' include 'they' (those are boys = they are boys).