Hi @AndyP_63,
As @jakaskerl has already mentioned, you can directly export the pre-trained Resnet50 from the OpenVINO model zoo. Here's the exported model. You can see the model card in the zoo here. The way this conversion works is that the blobconverter automatically downloads the source model from the zoo for you and exports it, so you don't have to upload the model yourself.
Regarding the opsets, with OpenVINO in version 2022.1, you can set opset to a value higher than 8; for example, in our tools.luxonis.com (our tool for converting YOLO models), we use opset 12.
Best
Jan