It's a bit typical for non technical person. Let me answer you, and you can try to make changes In it.
The GL account codes are initially stored in chart_master table. From there we used to make GL and journal entries. That will store in gl_trans table. And then it can be connected with bank accounts in bank_accounts table. If any GL settings connected to that GL account it must be in sys_prefs table. And if you made supplier invoices with GL accounts, you need to look in supp_trans table. The same way with customer deposits and supplier payments through journal entry. It will also hit the gl_trans table. So take it seriously and check it those tables to find and replace the gl account code manually with help of MySql client like phpmyadmin or workbench. May be If i miss any table add further comment. So someone will get benefited in future by accessing this post.
Good luck.
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