Hello! You can view the rules for Super Mario Bros. 3 on there src page here: https://www.speedrun.com/smb3

Click on the category you would like to submit too and click "View Rules." Any questions should be directed towards the game's moderators. You can see them in the bottom left with the red, green, and yellow swords.

General site rules regarding run submissions: https://www.speedrun.com/rules#ch6_Submitting_a_Run