When you are speaking to two or more people ‘dere’ is the personal pronoun used.
Hva heter dere?
Hvor kommer dere fra?

but also say

When you are speaking about two or more people ‘de’ is the personal pronoun used.
Hva heter de?
Hvor kommer de fra?

can you clarify??

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from L-Jay:

dere – plural you
‘dere’ is a second person dual/plural pronoun – meaning: when you are talking to two or more people. eg: ‘you two’ or ‘all of you’, as in ‘Where do you two come from?’ or ‘Where do all of you come from?’
(At a more advanced level you will understand that ‘deres’ also mean ‘yours’ and ‘theirs’.)

de – they
‘de’ is a third person plural pronoun – meaning: when you talk about two or more people. eg: Where do they come from?

I’ve just highlighted the ‘abouts’ and ‘tos’ in that section of the lesson to make it easier to understand