SELECT CAST(SUBSTRING(myStringWNumber, posNumStart, posNumEnd), <NUM_TYPE>) FROM table;
<NUM_TYPE>
SIGNED Converts value to SIGNED (a signed 64-bit integer)
UNSIGNED Converts value to UNSIGNED (an unsigned 64-bit integer)
BINARY Converts value to BINARY (a binary string)
DECIMAL Converts value to DECIMAL. Use the optional M and D parameters
to specify the maximum number of digits (M) and the number of digits
following the decimal point (D).