ETWS SIB 10 cannot be decoded by UE

Hi Experts,

I have a question regarding ETWS in LTE, the message length of sib10 comes to be 488 bits in my case, what must be the mcs index and number of PRBs for the required TBsize it needs? And which DCI format we should we use, DCI 1A or DCI 1C? Thanks you.