Select and Update MAC Addresses to Same Format
Test select: 

select macaddress, upper(replace(macaddress,':','')) as new_macaddress
from Macs;


Update:

update macs
set macaddress = upper(replace(macaddress,':',''));


Fiddle

Test data:

create table macs
(
macaddress varchar(20)
);

insert into macs values('90CCAADD3341');

insert into macs values('90:3f:ff:11:22:33');

insert into macs values('33:44:aa:bb:34:6a');

insert into macs values('8801abcd3231');


Documentation links:

UPPER()

REPLACE()