The 2018 data is not transferring automatically to 2019
the contacts are not showing or any other 2018 related data
Please explain your issue in more detail as it does not make sense.
QuickBooks is perpetual bookkeeping. Your data does not disappear from your one single company file just because the year rolls over. Data is not purged. Possibly if you are looking at reports or other screens it may have defaulted to display only current year but that is an easy selection