Your category will depend on whether your mother is a US citizen or a green card holder.
The adult son/daughter of a US citizen is in the F1 Preference category and in June 2020, the US Department of State (National Visa Center – NVC) will have visas available for those persons with a priority date earlier than May 22, 2014.
If your mother is a green card holder, your petition would be in the F2B category and in June, persons with a priority date earlier than March 15, 2015 would have visas available.
If you are eligible to change your status once a visa becomes available, your non-immigrant entry into the United States can be voided if you are thought to have entered the US with the intent of remaining until the green card is available.
Second, in your category, if you were in the United States and out of status when the green card becomes available, you would not be eligible to change your status with your mother’s petition.
