Let's talk box jumps!
Box jumps are a lower body (primarily) exercise used to build explosiveness, landing mechanics and force absorption. Box jumps are a valuable addition to any workout regimen, but they must be progressed according to fitness level, goals and experience.

In short, the average number of box jumps per workout should be 20-40 repetitions.

A person can do more or less, as this is by no means the law of the land.

This is my opinion deeply rooted in personal experience with athletes, my own training and my observation of modern evolution of box jumps.
Per https://movemoresitless.wordpress.com/2013/03/24/how-many-box-jumps-should-be-performed-in-a-workout/

New to working out?

Experts recommend three different types of exercise for overall physical fitness: cardiovascular activity, strength conditioning, and flexibility training.
Cardiovascular activity. Start by doing an aerobic activity, like walking or running, for a sustained 20-30 minutes, four to five times a week, says Bryant. Make sure you can carry on a basic level of conversation without being too winded.
Strength conditioning. Start by doing one set of exercises targeting each of the major muscle groups. Bryant suggests using a weight at which you can comfortably perform the exercise eight to 12 times in a set. When you think you can handle more, gradually increase either the weight, the number of repetitions, or number of sets.
Flexibility training. The American College on Exercise recommends doing slow, sustained static stretches three to seven days per week.
Reference Credit webmd.com

Why physical activity is important, especially now!

According to the Centers for Disease Control and Prevention (CDC), getting enough physical activity could prevent 1 in 10 premature deaths, yet only half of adults get the physical activity they need to help reduce and prevent chronic diseases. Exercising could also prevent:

1 in 8 cases of breast cancer
1 in 8 cases of colorectal cancer
1 in 12 cases of diabetes
1 in 15 cases of heart disease. Photo and article credit: https://www.scripps.org/news_items/6936-exercising-during-covid-19-pandemic-you-have-options

COVID-19: Exercise when ill; what’s okay and what’s not Per Mayo Clinic. Exercise is important for a healthy body and mind, but if you're feeling under the weather, you may wonder what's OK to tackle or if you should hang up your sneakers. Dr. Daniel Montero, a Mayo Clinic sports medicine physician, offers some advice for when to exercise. "Exercise is medicine. If you have symptoms above the neck, things like runny nose, sneezing, of the common cold, such as nasal congestion or runny nose, or minor sore throat, you're OK to exercise," says Dr. Montero.

"Exercise may even help you feel better by opening up your nasal passages, for instance. But you may want to reduce the intensity and length of your workout, and limit group activities," he says.

Instead of running, for instance, go for a walk. “Any amount of exercise has benefits,” says Dr. Montero.