wa'alaikum as'salaam,
It is something you can discuss with your guardian beforehand. Otherwise...
Deciding the amount of the dowry is to be left to the woman and her guardian. If the woman disagrees with her guardian about the amount of the dowry, then what appears to be the case from the words of the scholars is that they should take as a reference the dowry of a woman of similar standing. If she agrees to the dowry of a woman of similar standing, but he wants more than that, then no attention should be paid to his wishes. If he is the one who wants a dowry like that of a woman of similar standing, but she wants less than that, then what matters is his view.
https://islamqa.info/en/224876
If the marriage contract was done without any mention of the mahr, the marriage contract is valid and the wife is entitled to a mahr like that of her peers.
Marriage without stating the mahr is of two types. The first is that in which the mahr is not mentioned at all, and the man gives his daughter in marriage without any mahr, so he says: I give you my daughter in marriage, and the suitor says: I accept – without mentioning any mahr, as happened in your case.
The second type is that in which the mahr is mentioned without specifying its amount, such as if the suitor says to the wali: I will give you what you want of the mahr, or the wali says to the suitor: Give whatever you see fit, and so on.
The wife is to be given a mahr like that of her peers in both cases.
The mahr of her peers is to be defined by the qaadi (judge), so as to avoid conflict. But if they agree on something without referring to the qaadi, there is nothing wrong with that, because they have the right to do so.
https://islamqa.info/en/111127