Preboarding when converting CW to Employee

The situation is that the Contingent Worker never went through the pre-boarding step where we collect banking, tax, superannuation information – this occurs in the pending worker stage (i.e. before they commence on day 1 and are assigned on Onboarding Journey) only in the case of Employee Hire. When the Contingent Worker is converted to Employee, they can be assigned an Onboarding Journey, but we don’t have their banking, tax, superannuation information because this was not collected from them originally. 

How to trigger Preboarding When the Contingent Worker is converted to Employee?