Could not Convert String to Float w/ADNI classifier

import pandas as pdimport numpy as np# Load the datadata = pd.read_csv("/content/ADNI1_Complete_3Yr_3T_1_31_2024.csv")# Split the data into features and labelsX = data.drop("Group", axis=1).valuesy = data["Group"].values# Encode the labelsfrom sklearn.preprocessing import LabelEncoderencoder = LabelEncoder()y = encoder.fit_transform(y)# Split the data into training and testing setsfrom sklearn.model_selection import train_test_splitX_train, X_test, y_train, y_test = train_test_split(X, y, test_size=0.2)# Normalize the dataX_train = X_train.astype("float32") / 255.0X_test = X_test.astype("float32") / 255.0

This CNN is outputting the ValueError could not convert string to float: 'I120798'. I am using an ADNI dataset. The section of normalizing the data is outputting the error. I expect this to begin training a CNN. What should I change in this code in order to begin training the CNN with the dataset.