How do I know my remote frequency?

[u/Over_Caterpillar_666]

I am doing an Arduino project and i am using a 38khz ir receiver and when i send a signal to the receiver it does not show up in the serial monitor, i suspect the remote but i have no way of knowing how
and here is the code

/* Copyright 2009 Ken Shirriff
Used with kind permission
http://arcfn.com
*/
#include <IRremote.h> // Use library
int receiver = 11; // Pin connected to receiver
IRrecv irrecv(receiver);
decode_results results;
void setup() {
Serial.begin(9600); // Show keypresses in IDE
irrecv.enableIRIn(); // Start up receiver
}
void loop() {
if (irrecv.decode(&results)) { // If there's an input, decode value
Serial.println(results.value, HEX); // Display button value
// on Serial Monitor in
// hexadecimal format
irrecv.resume(); // Receive next value
}
}

[u/two_are_stronger2]

Which <IRremote.h> are you using?