Down load all the historic ticks data from a pair. Just load the EA to a graph, give it time to download all the data ticks and wait for the messages to appear as downloaded in the terminal. Once its downloaded, the data will appear in MQL5/Files folder as "ticks_data_XXXX.csv". where XXXX is the symbol from whom you just downloaded the data. You can use this data as input for a python file for ONNX or what ever you want or need. For big pairs, the data is Gb big.