The unexpired visa in your expired passport remains valid, and you can continue to use your existing visa to enter the US, without getting a new visa, as long as you use it with a new passport of the same type and issued by the same country as the old passport.
FAQ from the Department of State:
My old passport has already expired. My visa to travel to the United
States is still valid but in my expired passport. Do I need to apply
for a new visa with my new passport?
No. If your visa is still valid you can travel to the United States
with your two passports, as long as the visa is valid, not damaged,
and is the appropriate type of visa required for your principal
purpose of travel. (Example: tourist visa, when your principal purpose
of travel is tourism). Both passports (the valid and the expired one
with the visa) should be from the same country and type (Example: both
Uruguayan regular passports, both official passports, etc.). When you
arrive at the U.S. port-of-entry (POE, generally an airport or land
border) the Customs and Border Protection Immigration Officer will
check your visa in the old passport and if s/he decides to admit you
into the United States they will stamp your new passport with an
admission stamp along with the annotation "VIOPP" (visa in other
passport). Do not try to remove the visa from your old passport and
stick it into the new valid passport. If you do so, your visa will no
longer be valid.