There is no possibility to convert the Rockwell hardness to Vickers or Brinell hardness.
However, hardness comparative tables (table 1) enable comparison of hardness values according to all three test procedures with the strength according to DIN EN180 18265 (2004-02).
The table values are guide values. The comparison of hardness according to the various test procedure is always prone to errors. If possible, it is to be avoided. However, this comparison can never be fully excluded. This particularly applies for the conversion of hardness values to strength and vice versa.
Tensile strength/Hardness quotient