Because there are several convictions, you would not be able to apply for deemed rehabilitation at the POE. You would have to apply for Individual Rehabilitation through a Canadian Consulate.
The Individual Rehabilitation process can be lengthy and often takes more than a year to process. If you have not applied for a pardon/expungement/ record suspension in the jurisdiction where you were convicted, then begin the process now. Also, ensure you have all your court documents, parole officer notes, sentencing documents and any other supporting information regarding your past convictions, penalties and proof of completed sentences.
Because you are currently considered inadmissible, you will not be able to obtain a Canadian Work Permit unless you obtain a TRP first. There are no guarantees that you will be granted a TRP, as the Officer considering your application will weigh your reasons for entering Canada versus the risks to Canadian citizens and permanent residents. The Officer will consider if there is a compelling need for you to be in Canada, usually this would be some economic benefit to a Canadian employer or a specific event, like presenting at a conference.
If you are not sure if you are inadmissible, it is best to have your records reviewed by someone familiar with Canada’s criminal and immigration law to guide you through this process.