about the free expo build package that is given 30build/month…
if I enter in the next month, will I still get another 30 builds again?

For example, if my build in April was 30 builds, will I get another 30 builds in the next month (May)…?

>Solution :

Yes, you will get these 30 builds each month.

Just some thoughts: If you plan to use Expo in a professional way, you should keep in mind, that 30 builds are not that much. For example, if you are building 2 apps consecutively and create nightly-builds for each one, you will very soon exceed this limit.
Also with the free plan, you may encounter very long queue times for your builds. My maximum queue time, as far as I remember, was more than 6 hours. If you are in a hurry fixing security issues, this can be a very long wait time for you and your customers.