Please Follow Following Step:-

– Download New Vanilla 2.3 installer
– Install Vanilla 2.3 into localhost
– copy all folder (everything except conf/, cache/, uploads/, custom themes/and custom plugins/ htaccess)
– before paste delete all folder from old vanilla (except conf/, cache/, uploads/, custom themes/and custom plugins/ htaccess)
– paste all folder on old vanilla folder and change in following file
– delete .ini files from cache folder
– In Browser http://localhost/projectName/vanilla/utility/update
– Copy and paste plugins folder from new vanilla