What is the ruling on buying (dollar) currency that is impounded or stolen, which was offered for sale to me to face debts and a difficult financial situation as a refugee?

It is not permissible to buy goods that are highly likely to be plundered or stolen, because they are not owned by their seller. Buying them is considered participation in sin and injustice, and cooperation in sin and aggression.

An exception to this is if the purchase is for the purpose of recovering the money and returning it to its owners, or giving it as charity on their behalf, or spending it on the welfare of Muslims if its owners cannot be identified, as explained by Shaykh al-Islam Ibn Taymiyyah.

Whoever knows that a commodity is stolen should advise the thief. If the thief does not desist, then he should report it to the competent authorities to restore rights to their owners and to apply the حديث (Hadith): "Help your brother, whether he is an oppressor or oppressed." Helping the oppressor means preventing him from his oppression.