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how to make database store 6 digit input

Do the Bubble tutorials. This is a basic function.

Satu lagi bagai mana cara agar semua inputan kita terima notifikasinya di email. Apakah ada plugin khusus

Use the Send Email function.

how to do it, please give me a way so that my email receives notifications

Literally click the Send Email workflow and fill in the details.

Like in my previous answer, I highly recommend learning the fundamentals of Bubble.