Posting Explorer is the Ledger view, but I don’t see any reconciliation format at top of the screen.

In the Reconcile column I do have items reconciled, such as: 2040101, 2040102, etc.
These are the NV1 codes when we imported the data.

If I wish to use 20510-01-01 as the new code(rather than 2051001), how do I get nv2 to recognize this as the new format? Don’t tell me I have to change the old ones!