Course content created in Blackboard can be imported in Canvas by following these steps:
Remove Excess Grading Categories from your Blackboard Grade Center
Open the full Blackboard Grade Center
Go to Manage and choose Categories
You may see several empty grading categories. These appear and multiply each time you copy Blackboard content from one semester to the next. While these categories do not affect Blackboard, they can cause serious issues with the Gradebook and Assignments page in Canvas and, therefore, must be removed.
To remove the excess grading categories, click “show all” at the bottom of the page

Next, click on the box to the left of the word “title” (this will “select” all empty grading categories) and click delete to remove excess grading categories.

Here is a video demonstration of this process.
Create Export Package
Once you’ve deleted the excess grading categories, you’ll need to create an Export Package (zip file) with your course content that can be imported into Canvas.
First, go to your Blackboard Control Panel and click on Packages and Utilities:

Choose “Export/Archive Course” and click on “Export Package.”
From there, choose the content you would like to import into Canvas. You may select “all” or choose individual content areas and tools:

Click “submit.”
When your Export Package is ready, you will receive an email message in your UIS email which tells you “the operation has been completed.”
When you go back to Packages and Utilities > Export/Archive course, you will see the Export Package ready to download.

Click on the link to save it to your downloads.
Import Your Content to Canvas
Open your Canvas course.
On the right side of the home page, you will see a button called Import Existing Content:

Under Import Content, select your content type (Blackboard 6/7/8/9) from the dropdown menu:

Under “source,” choose the Blackboard Export File from your downloads. Choose “all content” or “select specific content” and then click “import.”
You’ll see a green indicator when the process has completed:

You’ll then be able to begin creating, rearranging, and updating your Canvas modules with your newly imported content.
Note: Canvas courses have a size limit of 500 MB. Export packages larger than 500 MB will not import properly. If your course exceeds the size limits, you may need to upload videos to Kaltura and/or move files to Box which can be shared to Canvas.