EXCEL - VBA Coding - Data Entry Userform - assistance

I am looking for immediate EXCEL VBA Userform Coding assistance with the following 2 points:-

1- Assistance with adjusting code (automated, alpha Numeric, sequential numbering)on Excel 'Contacts' data entry Userform (with list) - need existing Userform VBA code formatted to reflect ="C" & TEXT(ROW()-1,"00000")

2 - VBA Userform - NEW Data Entry form to populate Purchase Order (automated as much as possible using data from worksheets in same workbook)- Have worksheet data column headings & Invoice Template already in workbook

Notes:
Hopefully Looking to build relationship for further assistance and ongoing help & support with areas - system -will be a simple WMS, CRM, Inventory control & product tracking database built in Excel initially using Worksheets as database with Macros & Userforms - attempting to make system as user friendly & simple (automated for user where possible) for multi-users as possible. Eventually possibly separating out and loading database to Google Sheets and sharing through Dropbox for 'multi-user' functionality or turning into web based api to be used by our VERY small business.

Many thanks
Debbie Steel