At what point/stage in install.php does it kick out that error?
Any of the info collected in the prompts to fill out DB info could cause that error if filling out in-correctly - including non-existent 'blank' DB to be used for the moodle.
Suggest you see (or re-read if you have already seen) and check your steps:
https://docs.moodle.org/310/en/Installation_quick_guide
'Create a Database' section?
'SoS', Ken