Hi Gabriel,
Sorry to hear about the lay-off. Usually the first tier to proving ServiceNow competence is to obtain the Certified System Administrator certification. There is a self-paced option for this class so you don't have to pay the full amount for an instructor-led class.
ServiceNow has a program called "Rise Up (https://www.servicenow.com/company/riseup.html). I don't know much of what it entails, but definitely see if you can benefit from it one way or another.
Finally, ServiceNow talent is in very high demand. Your 15 years in the ITSM field should be a huge asset, despite your lack of ServiceNow experience. I recommend also trying to obtain your ITIL 4 Foundations certification to further prove your knowledge and expertise.
Even without the CSA and ITIL 4 Foundations certifications (as long as you have these in process...they should be considered required for the field), I recommend starting to research companies that provide ServiceNow implementation services. There are lots to choose from (start here: https://www.servicenow.com/partners/partner-finder.html) and I believe they all will offer continuous learning opportunities as you continue to grow.
Please feel free to contact me directly in case you have any questions or need additional guidance.
