'PORT' is not recognized as an internal or external command

[lovelyplanet2019]

C:\Users\a\Downloads\snmp-sim-ui-main>yarn start port=5000
yarn run v1.22.22
$ PORT=5000 react-scripts start
'PORT' is not recognized as an internal or external command,
operable program or batch file.
error Command failed with exit code 1.
info Visit https://yarnpkg.com/en/docs/cli/run for documentation about this command.nd.