Detectives did two drug raids in New Bedford last week.   The first was at an apartment at 431 Union Street, and it led to the arrest of 2 people.   Police also seized a loaded .357 revolver, heroin and cocaine, and over $1400 in cash.   They arrested 21-year-old Michael Cardozo.  In the second raid at 46 Belleville Road, detectives found heroin, cocaine, and more than $2,200 in cash.  34-year-old Renee Perez was arrested and charged with trafficking.   Police say the combined street value of the drugs seized in both raids is $36,000.