Order of integration is only known through stationarity test. Besides there is no general order of integration for all the variables. Individual variables have their own order of integration. This is the first to do to know the statistical properties of your variables and the appropriate model to use.
So first thing first. Use the ADF or PP test or others in literature to determine the order of integration of each of the variables ( also known as test of stationarity). The result from here will determine whether to use VAR or VECM.
Use VECM only if ALL the variables are known to be integrated of order 1 and they are ALL stationary after differencing (that is they are cointegrated). The rest is considering VAR at level or VAR at difference or Toda and Yamamoto (1995) VAR of integrated series of different order.