Here is a trigger I wrote. I understand that I need to get the conversion rate SOQL query out of the for statement:

trigger OpportunityBeforeInsertUpdate on Opportunity (before insert, before update) {


for(Opportunity opp : Trigger.new) {
    if (opp.Total_Amount__c > 0) {
        opp.Amount = opp.Total_Amount__c;
        system.debug('opp amount is ' + opp.Amount);
        } 
    
    
     if(Trigger.isInsert 
     || 
     ((opp.Amount != Trigger.oldMap.get(opp.Id).Amount || opp.CurrencyIsoCode != Trigger.oldMap.get(opp.Id).CurrencyIsoCode)
     &&
     (!opp.IsClosed || (opp.IsClosed && !Trigger.oldMap.get(opp.Id).IsClosed)))
     ||
     (!opp.IsClosed && Trigger.oldMap.get(opp.Id).IsClosed)
     ) 
         {
   double conversionrate = [select conversionrate from CurrencyType where IsoCode = :opp.CurrencyIsoCode];
            opp.Amount_USD__c = opp.Amount/ ConversionRate ;
        }
}
}

 so I wrote the following but still get the Too many SOQL queries error when running a test where 200 opps are inserted:

trigger OpportunityBeforeInsertUpdate on Opportunity (before insert, before update) {

List<CurrencyType> currs = new List<CurrencyType>
([select id, IsoCode, ConversionRate from CurrencyType where IsActive=true limit 200]);

Map<String, Decimal> ConversionRates = new Map<String, Decimal>();

for(integer i=0; i<currs.size(); i++){
ConversionRates.put(currs[i].IsoCode, currs[i].ConversionRate);
}


for(Opportunity opp : Trigger.new) {
    if (opp.Total_Amount__c > 0) {
        opp.Amount = opp.Total_Amount__c;
        system.debug('opp amount is ' + opp.Amount);
        } 
    
    
     if(Trigger.isInsert 
     || 
     ((opp.Amount != Trigger.oldMap.get(opp.Id).Amount || opp.CurrencyIsoCode != Trigger.oldMap.get(opp.Id).CurrencyIsoCode)
     &&
     (!opp.IsClosed || (opp.IsClosed && !Trigger.oldMap.get(opp.Id).IsClosed)))
     ||
     (!opp.IsClosed && Trigger.oldMap.get(opp.Id).IsClosed)
     ) 
         {
            opp.Amount_USD__c = opp.Amount/ ConversionRates.get(opp.CurrencyIsoCode) ;
        }
}
}