Per this BBC article, the athletes will receive medals that were stripped from the banned competitors:
Britain's 4x400m relay squad from the 2008 Beijing Games got their
podium moment in front of a home crowd at the London Anniversary Games
last month, finally becoming Olympic medallists after a nine-year
They are among dozens of athletes who are receiving medals after their
competitors were disqualified retrospectively and stripped of their
achievements because of doping offences.
The new approach of the International Olympic Committee (IOC), as part
of a stated commitment to supporting clean athletes, is to "honour
accomplishments in a more systematic manner".
In the article, the writer interviewed a number of athletes that were suddenly Olympic medalists, often years after the fact. Some athletes received another medal ceremony in front of fans, another actually received a gold medal at a food court!
These competitors were naturally delighted to receive their medals, but also had mixed emotions - some had lost training support that would have been granted as a reward for medaling, and several missed a chance to receive an acknowledgement in front of an Olympic crowd at the competition.
Finally, the article notes:
The IOC says the reallocation process is not automatic and is done on
a case-by-case basis.